Recent developments in packaging technologies for integrated circuits have introduced a through-silicon via (TSV) which is a vertical electrical coupling passing through a silicon wafer or die. TSV is important for creating 3D electrical packages such that conductive layers can be stacked on top of one another and a signal can pass between the conductive layers by utilizing the TSV.
In a conventional packaging design, there can be an array or cluster of TSVs for passing signals between different conductive layers. Besides occupying space in the substrate, the TSVs can also affect the functionality of adjacent or nearby TSVs. For example, mutual inductance between nearby TSVs can cause cross-talk, which in some instances can negatively impact the operation of the electrical package. To reduce the effects of mutual inductance, the space between nearby TSVs is increased and complex calculations based on current densities of signals passing through the TSVs and the frequencies of these signals are required to ensure proper operation of the electrical package.
Another design challenge associated with a TSV is the creation of eddy current losses in the substrate. Eddy currents are formed in the substrate due to changing magnetic fields. As electrical current passes through the TSV, for example, magnetic and electric fields form around the TSV and penetrate the substrate. Changes in the current passing through the TSV may cause changes in the magnetic and electric fields within the substrate. Eddy currents can create an induced magnetic field that opposes the changes in the magnetic field in the substrate. Due to the relatively high resistivity of the substrate, the eddy currents dissipate into the substrate and can generate heat within the substrate. An insulating material can be disposed between the substrate and conductive layer, which can reduce the electric field and attenuate the effects of the magnetic field. However, eddy current losses still remain a problem.
Therefore, it would be desirable to reduce eddy current losses within the substrate and reduce the effects of mutual inductance between nearby TSVs without increasing the space between TSVs.